Chain Tensioner Opinions on Modifying the Stock Tensioner, V-Frame Engines

Discussion in 'Transmission / Drivetrain' started by Email, May 26, 2010.

  1. Email

    Email Member

    Chain Tensioner Link

    (I know the tensioner is a problem on these kits... I have read plenty of forums on the problems) I too have been having a problem with the chain tensioner that came with my Skyhawk kit I purchased from Spookytooth. This was the 66cc kit that they stopped selling, probably due to the EPA import restriction. The tensioner keeps sliding back down loosening the chain. To the best of my knowledge the sprocket on the rear wheel is centered; therefore, it is not a wobbly sprocket pulling it loose but instead the tug of the engine on the chain. The freewheel portion of the tensioner will no longer tighten, nor will it loosen (but freely spins and the wheel assembly slides up and down the slot if you wiggle it by hand) so it is stuck moving up or down in the slotted groove on the tensioner housing. I know I have a few options.

    The first option is to replace it with the mods mentioned on the forums (with a spring tensioner). Though the problems with spring tensioners are that it makes it more difficult to pedal start the engine.

    The second option is to replace the 410 chain with #41 chain and use halflinks and avoid use of the tensioner altogether.

    The third option that I thought about after really looking at the setup is to take a small metal bar, drill a partial hole so that the end of the bolt on the freewheel pokes into it (does not have to go through all the way, just grips it enough that it keeps the tensioner at the correct height). Next drill either a slotted hole (where I can adjust the tensioner height slightly) or a precision hole at a distance low enough that the top frame bolt will go through. I know I will have to replace this frame bolt with a longer one.

    If I go with the third option there's more that I can do to the bar to help prevent the tensioner from ever going into my spokes. I could make an I-beam with slots on either end that fit onto my rear drop out and bottom bar at a diagonal. In the center I can bolt into the bar I would make for the third option.

    Thoughts, opinions? Need a visual diagram/photo? I am not sure whether the third option gives me any advantages over what option 2 would give me, other than it provides another support structure for the chain itself and a mounting point for the chain guard?

    Last edited: May 26, 2010

  2. GearNut

    GearNut Active Member

    I wish I had a photo of what I am going to try to explain.
    some folks weld or clamp a strip of stout flat strap between the chain stay and seat stay.
    Determine where the tensioner wheel will rest when attached to said flat strap and cut an adjustment slot in in the strap. Attach tensioner wheel securely, with chain properly tensioned, in slot and ride happy and safe.

    Another method is to cut the engine's chain down suitably as to not need a tensioner for the engine chain, 1/2 links can help in doing this. If needed, use a tensioner on the pedal chain instead.
    Last edited: May 26, 2010
  3. Thatperson

    Thatperson Member

    I know what you are talking about. I built one for my Uncle's bike. It works a whole lot better than the stock setup.

  4. GearNut

    GearNut Active Member

    Thank you Thatperson!!!
  5. Email

    Email Member

    Cheap Quick Fixes

    Well I let eagerness get the better of me yesterday. I loosened my tensioner, slid it as far back to the rear wheel as I could and rode it around looking for a piece of my rear rack that had fallen off a few days ago (I remember hearing a pinging sound when I was driving it, but the bike was running fine so I had ignored it, still did not find it). Well the tensioner held up until I got home but when I got back I noticed it was extremely close to the spokes -><- like that much room from being a real problem. Well I loosened it back up again, pulled it back out, tightened it back down and was going to test it when I pulled the clutch to take off(bam) I ripped one of the 12G spoke nuts thru the rear rim and flipped the tensioner all the way to the bottom of the rear dropout. Hindsight, the bottom dropout tapers down back there so there was not enough metal to metal grip to hold the tensioner securely. I am so lucky it happened at home instead of when I was driving around looking for that piece of metal bracket.

    Now I have to rebuild a rear wheel (or order one built up). I think the rear hub is fine, but what I would like to get since I have yet to order a front brake hub is to see if someone like huskybicycles could put a wheel together for me. I really would like a 26x2.125 11G or 12G 3W Dyno 90mm Front Drum & a Rear Internal Geared Coaster so once I get the bike going properly I could build some electronics to take advantage of the power coming off the front wheel and gearing off the rear wheel. The only thing that semi-concerns me if I get the tensioner setup corrected is whether the front springer fork will be safe with a front drum brake. I also wish the rear hub had the capability to bolt on a sprocket vs the gasket sprocket method. You cannot get everything you want though. I know the cheap solution would be to replace the rear rim only, but cheap solutions do not always equal the best one. *sigh* back to driving the car again... it will be one to a few weeks before I can put the time back in to fixing it. A lot to think about for version 2, at least I got to get my feet wet and see what this hobby is about (playing with the gas, clutch & pedals on takeoff is fun - and because I love bicycle maintenance <3 the hobby even more). Got some stuff to do before I get that rear wheel though (if that's the option I decide to pursue), as I need to do some measurements (hub width, chain ring position, etc). May just build it on my own, so if it does break the only person I can blame is me.

    P.S. ThatPerson - NICE!

    Front Wish:
    Sturmey Archer: XL-FDD (redrilled for 12G)

    Rear Wish:
    Sturmey Archer (Measurement Dependent)
    Last edited: May 27, 2010
  6. arkives1

    arkives1 Member

    opinions on modifying the stock tensioner

    Please tell me where you found the straps with the rubber sleeve around them? I know I saw them somewhere, maybe on a scooter or electric bike site but cannot seem to find them again. I plan to do one of my cruisers the way you did your Uncle's.
    Thanks! Woody
  7. Email

    Email Member

    Rubber Cushioned Loop Straps: If you cannot find them anywhere else, there's always McMaster.

    I wonder if an Idler Sprocket would be better than the stock tensioner, but mounted like ThatPerson did, look at the ones with Wide Hubs(expensive-prob use offset washers and normal sprockets to get correct distance)? If you wanted you could put both one above and one below, would that not reduce chain wiggle?

    (Dyno Links for me later on: Complex Charging Circuit:
    (E-Werk Charger for USB:
    (Another USB From Dyno Option:

    (#40 vs #41 Chain) - Either work as a replacment to 415 Chain
    data of ANSI standard B29-1 (Precision Power Transmission Roller Chains, Attachments, and Sprockets).
    ANSI B29-1 roller chain standard sizes
    Size Pitch Roller diameter Tensile strength Working load
    41 0.500 in (12.70 mm) 0.306 in (7.77 mm) 1,500 lb (680 kg) 500 lb (230 kg)
    40 0.500 in (12.70 mm) 0.312 in (7.92 mm) 3,125 lb (1,417 kg) 810 lb (370 kg)
    Last edited: May 27, 2010
  8. GearNut

    GearNut Active Member

    Rear hubs are available that allow you to bolt the rear sprocket directly to them. They are not 3-speed though.

    Manic Mechanic can also machine you a custom rear sprocket mount that will clamp around the 3-speed hub of your choice.
    Here is an example from pirate cycles, see the top row.
    They can work with you to insure that the 2 piece adapter will fit perfectly on your 3-speed hub, or you can contact Manic Mechanic directly.
    Note that he does these as a hobby so you may have to wait a month or two to get it direct from him.
  9. Thatperson

    Thatperson Member

    I bought the straps at Lowes. Go into the hardware section and go over to where the specialty drawers are and look there. As far as lining up the pulley for the chain, it lined up perfect on the first try. I didn't have to add spacers or anything, you might not be that lucky, but it shouldn't be hard at all to do it. And I can tell you that if you pull this thing into the spokes, something went horribly wrong! :grin5:
  10. Email

    Email Member

    Here's the link if you want to write down the item/model numbers before you go to Lowes (Rubber Clamp in Search Pulls it up).

    GearNut - Thanks for the links! The kit from Bicycle Engines, is that freewheel sprocket the one for the peddle chain or for the motor chain? The Pirate Cycles would work on my Shimano if I have not messed up my hub. Any experience with either kit?
    Last edited: May 27, 2010
  11. a/c man

    a/c man Member

    Here's the way I did mine before the shift kit made it unnecessary.
    Flat 1 1/2" bar stock from home depot $6.50 for a 3 ft piece
    Took a good quality skate board wheel (my son has plenty)
    These wheels have really nice sealed bearings (2 sets in each wheel)
    Chucked it up in the Dewalt drill using a mandrel designed to use those
    cutting wheel attachments for electric drills.
    Clamped the drill to the work bench and held a 5/8" wide file against the roller wheel until it cut a channel in the wheel about 1/2" deep .
    I mounted the flat bar to the chainstay and seatstay using the original U shaped clamps that came with the stock tensioner. I cut the adjusting groove in the bar using a series of adjacent drilled holes, then filed out the spaces between the holes to make a slotted hole for the wheel to bolt thru.
    It worked really well and I used it for over 350 miles before I didn't need it anymore. Ditch the stock junk chain and get a good #41 chain that won't stretch and self-destruct.

    Attached Files:

  12. GearNut

    GearNut Active Member

    The freewheel is for the engine chain. It does makes it pretty hard to pedal start the engine so they also offer a solid mount, at least they used to. It has been a loooong time since I have looked around at what all they sell nowadays.

    The only experience I can share it what others have said.
    Some love it, others break it.
    I do want to run the Bicycle engines hub in the future.
  13. Email

    Email Member

    Because I currently have a single speed (and might go to an internal 3+ speed hub), do you think a shift kit would be a workable solution or do you think the engine would have too much torque for an internally geared hub?

    Secondly if I keep it a single speed, do you think a shift kit would be a waste of not just $$$ but capability?

    Ok further reading tells me I will probably be going with the following...
    1) SBP Deluxe Shift Kit ($250)
    2) X-RD8 : 8 Speed Rear Hub, 70mm Drum (~$170) with Shifter, Cables, Etc. (325% range of gearing, should probably go with a hill climbing SBP setup vs speed) - IF IT FITS IN DROPOUTS
    3) X-FDD : Front Drum Dyno (~$80)
    + other bits and pieces...
    Last edited: May 28, 2010
  14. a/c man

    a/c man Member

    Why would you consider buying a shift kit if you have a single speed hub?
    I don't know much about the internal hub's feasibility, but I know getting a Mega range freewheel would delight your bike riding senses.
    Seven speeds will take you wherever you'll want to go. From a dead stop without peddling to 40 mph and scare the **** out of you.
    Trust me it's like getting the Christmas present you always wanted
  15. Tinsmith

    Tinsmith New Member

    Tensioner Fix

    I never used the stock chain. Got #41 chain and mounted a sprocket instead of the roller on a spring-loaded tenisioner from Tractor Supply, and mounted it on the seatpost downtube so it couldn't get into the spokes if it moved. Been riding it for over a year and haven't made any adjustments. I did add another helper spring so it stays pretty tight, but it gives when it has to. Hope this might help. Dan
  16. Email

    Email Member

    Current Hub is a CB-E110 is a 109mm hub. No go on the 8 speed hub, too big. Also 1" seat tubing means SBP Shift kit won't work without shimming (smallest is 1.125", unless Ghost0 would make one smaller).

    I should be able to squeeze a S-RF5 hub (111mm) into the rear bracket (freewheels, no brake)... but seems that's going to be a hard one to find.
    Last edited: May 28, 2010
  17. GearNut

    GearNut Active Member

    I have never heard of a multi speed rear hub lasting. They all blow up. They cannot handle the torque load that an engine places on them.
    The only exception is a Nu-Vinci hub, which are pretty expensive. They do not have any gears inside them to blow up. The only draw back to them that I know of is they are 90% efficient. You loose 10% of input to internal slippage. So far all the reports I have heard from folks that run them is that they do not notice any slippage at all, but compared to a multi-speed sprocket setup, you will notice a tiny reduction in gas mileage.
    I have heard of only one person that burned up a Nu-Vinci, and he was pushing 5 HP through it. They obviously have their limits.
    And video of how it works:
    Here's a link to Sheldon Brown's site concerning it too:
    Staton-Inc. sells Nu-Vinci kits:

    I want one some year.......
  18. Email

    Email Member

    Thanks Gearnut, that's what I wanted to hear (I vaugly remembered some threads about internals not holding up, but that has been years ago and could not dig up any posts via search). I think with the limited overnut space, this bike just is not up to snuff for what I want to eventually do down the road. It is however, the only one I have that I am willing to put an engine kit on so I am going to stick with what I had originally planned for it. Add a front drum brake (keep it simple & cheap), and replace/fix the rear wheel, and do the tensioner mod with the metal bar from the bottom of the rear dropout to the top of the rear dropout. I will see if I can find a rollerskate wheel cheap at a thrift store this weekend. Thanks again guys, I appreciate the input.

    I will keep the thoughts of the NuVinci, SBP Shift Kit, etc. all in mind if I come across any other bikes that look viable to mod.
    Possibly one in the shed - CyclePro Pocono, ugly blue paint though. 132mm measured b/w the dropouts, V-Grip Brakes, 1.130in seat tube. Shimano SIS. It was one someone had tossed to the road for garbage to pickup. Sure is a cheap looking bike, made in Taiwan.
    Last edited: May 29, 2010